Abstract
The digestive stability of two natural antioxidant compounds present in virgin olive oil, hydroxytyrosol (HTy) and hydroxytyrosyl acetate (HTy-Ac) and a new series of hydroxytyrosyl ethers (methyl, ethyl and butyl hydroxytyrosyl ethers) was evaluated by a simulated digestion procedure. High recovery of all compounds after gastric digestion was obtained, although they showed a statistically significant lower stability after pancreatic–bile salts digestion. HTy-Ac was partially hydrolyzed into free HTy, whereas after intestinal digestion, HTy was converted into 3,4-dihydroxyphenyl acetic acid (DOPAC), and HTy-Ac was hydrolyzed to HTy and subsequently transformed into DOPAC. In contrast, no chemical modification of hydroxytyrosyl ethers during in vitro digestion was observed. In summary, HTy, HTy-Ac and hydroxytyrosyl ethers show high and interesting digestive stability and the new synthetic hydroxytyrosyl ethers showed enhanced chemical stability compared to HTy and HTy-Ac.
Acknowledgement
The technical assistance of M. López-Vilchez is acknowledged. This work was supported by Grants AGL2007-66373-C04/ALI and Project CSD2007-00063 (CICYT), and Grant RTA2007-000036-00-00 from (INIA) and a contract (110105090014) with CSIC–IFAPA.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.